Various etching processes are used in the fabrication of semiconductor devices. Such etching processes are used to control and maintain critical dimensions of various device structures such as, for example, transistors, capacitors, and interconnects. As semiconductor devices become more integrated and miniaturized, the maintenance and control of such critical dimensions of device structures becomes more important.
During the formation of semiconductor devices, such as dynamic random access memories (DRAMs), static random access memories (SRAMs), microprocessors, etc., insulating layers such as silicon dioxide, phosphosilicate glass (PSG), borophosphosilicate glass (BPSG), TEOS, or other oxides, are etched to form insulating structures, e.g., openings, used for various purposes. Such purposes may include the formation of capacitor structures, contact structures, interconnect structures, etc.
For example, with respect to interconnect structures, it is often required that conductive layers be interconnected through openings or holes in an insulating layer. Such holes or openings are commonly referred to as contact openings when the hole extends through an insulating layer to an active device area or vias when the hole or opening extends through an insulating layer between two conductive layers.
Further, for example, in the formation of certain types of capacitors, openings in insulating layers may be formed such that a capacitor structure may be formed therein. One illustration of such a capacitor structure is described in U.S. Pat. No. 5,392,189 to Fazan, et al., entitled "Capacitor Compatible With High Dielectric Constant Materials Having Two Independent Insulating Layers And The Method For Forming Same," issued Feb. 21, 1995. In this illustrative capacitor example, a storage cell capacitor is provided wherein electrodes are formed of a conductive material within high aspect ratio openings in an opening defined by a bottom surface and side walls in an insulating layer.
The profile of such structures is of particular importance, for example, such that desired characteristics are exhibited when further processing is carried out relative to the structure. For example, in many circumstances it is preferred to have openings or structures having near vertical profiles, e.g., at least one wall being near vertical. In other words, the slope of the walls defining the openings or structures have a slope that is very close to 90.degree..
For example, with respect to a contact hole or via, a near vertical wall defining the opening into which conductive material is formed provides a larger area at the bottom of the opening as opposed to an opening defined by walls that are less than vertical. Contact resistance for a contact formed in the opening is sensitive to the area at the bottom of the opening.
Further, for example, with respect to a capacitor structure such as a container capacitor illustratively described in U.S. Pat. No. 5,392,189 to Fazan et al., near vertical walls defining a container opening in which a capacitor structure is formed provides a significant increase in cell capacitance for a given height of a capacitor structure relative to a container opening defined by walls that are less than vertical. For example, an opening defined with near vertical walls extending from a bottom surface will generally provide a greater surface area upon which an electrode of a capacitor can be formed relative to a structure having sloped walls which are less than vertical, e.g., less than 88.degree. slope.
The etching of a structure or opening in an insulating layer, e.g., oxide layer, resulting in walls that are generally near vertical is difficult. This is particularly true with respect to high aspect ratio openings. It is known to utilize dry etch plasmas containing fluorocarbons or hydrofluorocarbons to etch oxides, or other insulating layers, relative to underlying conductive layers, e.g., silicon-containing layers such as doped silicon, polysilicon, or other conductive materials. For example, plasmas containing CHF.sub.3, C.sub.2 HF.sub.5, CH.sub.2 F.sub.2 and combinations thereof have been used to perform such an etch of insulating layers. Further, other gases may be mixed with the fluorocarbon or hydrofluorocarbon plasmas in the etch process to enhance the etch. For example, argon and helium are commonly used diluents typically used to dilute the chemical species and to stabilize the plasma when generated.
However, use of such conventional dry etch processing (e.g., plasmas containing fluorocarbons or hydrofluorocarbons) to etch openings generally result (at best) in walls which define the opening or structure having a slope of between 85.degree. and about 88.degree. relative to horizontal. Such a profile is, in many circumstances, undesirable when attempting to optimize the characteristics of the structure being formed, e.g., a capacitor, a contact, etc. Such a profile is particularly undesirable with respect to high aspect ratio structures.